Screw syringes of the type mentioned above are used for dispensing, in particular dosed dispensing, of a material. The materials concerned are in particular (but not exclusively) flowable and/or pasty dental substances or dental materials. In dentistry different materials are used in various applications. An example of these is tooth-coloring plastic filling materials with a plastic matrix and fillers, known as composites. Composites can have a highly viscous, packable consistency or a low-viscosity, flowable consistency.
Dental materials such as composites are normally sold in pre-filled screw syringes. Such a pre-filled syringe contains the material to be dispensed in a sleeve of the syringe barrel with a preferably partially or completely hollow cylindrical form. By operating the piston spindle the material is pushed out of the discharge end of the sleeve in an axial discharge direction, in that when the piston spindle is rotated by engaging the external thread of the piston spindle with the internal thread of the female part the piston spindle advances into the sleeve filled with material of the syringe barrel and thus expels the material from the sleeve.
In other application areas flowable and/or pasty materials may also be dispensed from a screw syringe, for example in welding, when applying pastes or in the application of adhesives or sealants.
In order to be able to drive the piston spindle in the sleeve of the syringe barrel in the axial discharge direction, the internal thread of the female part must have a smaller diameter than the sleeve of the syringe barrel. The female part with the internal thread must therefore be applied to or mounted on the syringe barrel. A screw connection between the female part and the syringe barrel has the disadvantage that when operating the piston spindle the screw connection between the syringe barrel and the female part can be unintentionally released.
Another possible connection can be achieved by a coupling mechanism in which the female part is slid in a radial sliding direction onto the piston end of the syringe barrel. Here the piston end of the syringe barrel refers to a section at the end of the syringe barrel into which the piston spindle penetrates, that is to say an area at the end of the syringe barrel that faces the discharge end of the sleeve. Screw syringes with a coupling mechanism can still be improved upon, however, in particular with regard to the reliability of the connection between the female part and the syringe barrel and with regard to simplification of the assembly process.